Microelectromechanical systems (MEMS) technology has achieved wide popularity in recent years, as it provides a way to make very small mechanical structures and integrate these structures with electrical devices on a single substrate using conventional batch semiconductor processing techniques. One common application of MEMS is the design and manufacture of sensor devices. MEMS sensors are widely used in applications such as automotive, inertial guidance systems, household appliances, game devices, protection systems for a variety of devices, and many other industrial, scientific, and engineering systems. Examples of MEMS sensors include inertial sensors and pressure sensors. Specific examples of MEMS sensors include gyroscopes and accelerometers.
The manufacturing of MEMS sensors is a complex task, relying on a variety of fabrication technologies and processes, and can involve the fabrication and combination of multiple semiconductor die. For example, in many cases it is desirable to encapsulate the MEMS sensor in a cavity. Such a cavity can be formed between two dies that together form the overall sensor device. The cavity allows motion of the MEMS sensor and is generally sealed to maintain a vacuum around the MEMS sensor. The configurations and fabrication techniques used to form such MEMS sensors, and form and seal the cavities that encapsulate the MEMS sensors, can be relatively complex and subject to unacceptable failure rates. Furthermore, the configurations and fabrication techniques can require relatively large areas of the device to effectively seal the MEMS sensors, thus limiting device density.
For these and other reasons there remains a continuing need for improved MEMS sensor fabrication techniques and device configurations.